7 Answers
7

The paid versions offer more features (i.e., puppet offers an easier way to deploy en mass) and, in many cases most importantly, paid support. When running enterprise servers, having paid support to help you get setup is typically worth it--especially when you run into issues.

Typically, you won't go wrong with the free versions... its only if you need help getting up and running, or you simply have such a large infrastructure (and little experience with configuration management).

I can only speak to my experience with Chef (which has been awesome). Chef is open source, you can use if for free, and they have good on-line documentation and wiki pages.

Chef has several 'flavors'. You can run the whole thing for free using Chef-Server (which requires you to set up the server software in addition to the client software on your system). Opscode also offers a hosted version (where they run the server for you) ... you can use the Opscode Platform for free for up to 5 nodes, after than you have to pay for the 'enterprise' edition.

Chef also offers a 'Chef-solo' version, that doesn't speak to a server, but I haven't found that to be very useful.

So, if you have less than 5 'nodes' (a node is a server you are administering) Chef is free. Or, if you want to go the route of hosting a Chef-Server.

Support has a fee, but the community is usually pretty good about offering advice.

I'm using puppet (the free one) to run a network of ~250 servers including VMs. It's great, but if I had it to do again, Puppet Enterprise might have been worth it. Time is worth money :) On the other hand, it looks like 250 nodes costs $17k annually!

There's a significant drop between initial cost and recurring support cost. We have a 250 node license and I want to say year 1 was ~$17k, but I requested a quote for subsequent years and it's ~$8k? I'm pulling these numbers from memory, but it was that drastic of a difference.
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Kyle SmithJan 29 '12 at 3:29

Interesting. That wasn't evident from the site, but it makes sense.
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Bill WeissJan 29 '12 at 12:50

I can't speak for Chef but I use Puppet where I work. There's an "enterprise edition" that comes with support but they also have a version that's totally free. Here's the link to the "open source" edition.

Most of the times you pay for support which these organizations provide. You can see the chart of comparison between puppet and puppet enterprise.
Having said that, several big organization are using puppet (not enterprise) and are totally happy with it. Being around for a little more time than chef, puppet has a bit mature community support and ready-made recipes free to use.

In short, feel free to go with non-enterprise version. There is a high probability that it'll fulfill your needs.